src/conflicts.c

   1 /* Find and resolve or report look-ahead conflicts for bison,
   2    Copyright (C) 1984, 1989, 1992, 2000 Free Software Foundation, Inc.
   3
   4    This file is part of Bison, the GNU Compiler Compiler.
   5
   6    Bison is free software; you can redistribute it and/or modify it
   7    under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 2, or (at your option)
   9    any later version.
  10
  11    Bison is distributed in the hope that it will be useful, but
  12    WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with Bison; see the file COPYING.  If not, write to the Free
  18    Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  19    02111-1307, USA.  */
  20
  21 #include "system.h"
  22 #include "getargs.h"
  23 #include "alloc.h"
  24 #include "files.h"
  25 #include "gram.h"
  26 #include "state.h"
  27 #include "lalr.h"
  28 #include "conflicts.h"
  29 #include "reader.h"
  30 #include "LR0.h"
  31
  32 int any_conflicts = 0;
  33 errs **err_table;
  34 int expected_conflicts;
  35 static char *conflicts;
  36
  37 static unsigned *shiftset;
  38 static unsigned *lookaheadset;
  39 static int src_total;
  40 static int rrc_total;
  41 static int src_count;
  42 static int rrc_count;
  43 \f
  44
  45 static inline void
  46 log_resolution (int state, int LAno, int token, char *resolution)
  47 {
  48   if (verboseflag)
  49     fprintf (foutput,
  50              _("\
  51 Conflict in state %d between rule %d and token %s resolved as %s.\n"),
  52              state, LAruleno[LAno], tags[token], resolution);
  53 }
  54
  55
  56 /*------------------------------------------------------------------.
  57 | Turn off the shift recorded for the specified token in the        |
  58 | specified state.  Used when we resolve a shift-reduce conflict in |
  59 | favor of the reduction.                                           |
  60 `------------------------------------------------------------------*/
  61
  62 static void
  63 flush_shift (int state, int token)
  64 {
  65   shifts *shiftp;
  66   int k, i;
  67
  68   shiftp = shift_table[state];
  69
  70   if (shiftp)
  71     {
  72       k = shiftp->nshifts;
  73       for (i = 0; i < k; i++)
  74         {
  75           if (shiftp->shifts[i]
  76               && token == accessing_symbol[shiftp->shifts[i]])
  77             (shiftp->shifts[i]) = 0;
  78         }
  79     }
  80 }
  81
  82
  83 /*------------------------------------------------------------------.
  84 | Attempt to resolve shift-reduce conflict for one rule by means of |
  85 | precedence declarations.  It has already been checked that the    |
  86 | rule has a precedence.  A conflict is resolved by modifying the   |
  87 | shift or reduce tables so that there is no longer a conflict.     |
  88 `------------------------------------------------------------------*/
  89
  90 static void
  91 resolve_sr_conflict (int state, int lookaheadnum)
  92 {
  93   int i;
  94   int mask;
  95   unsigned *fp1;
  96   unsigned *fp2;
  97   int redprec;
  98   errs *errp = (errs *) xmalloc (sizeof (errs) + ntokens * sizeof (short));
  99   short *errtokens = errp->errs;
 100
 101   /* find the rule to reduce by to get precedence of reduction  */
 102   redprec = rprec[LAruleno[lookaheadnum]];
 103
 104   mask = 1;
 105   fp1 = LA + lookaheadnum * tokensetsize;
 106   fp2 = lookaheadset;
 107   for (i = 0; i < ntokens; i++)
 108     {
 109       if ((mask & *fp2 & *fp1) && sprec[i])
 110         /* Shift-reduce conflict occurs for token number i
 111            and it has a precedence.
 112            The precedence of shifting is that of token i.  */
 113         {
 114           if (sprec[i] < redprec)
 115             {
 116               log_resolution (state, lookaheadnum, i, _("reduce"));
 117               *fp2 &= ~mask;    /* flush the shift for this token */
 118               flush_shift (state, i);
 119             }
 120           else if (sprec[i] > redprec)
 121             {
 122               log_resolution (state, lookaheadnum, i, _("shift"));
 123               *fp1 &= ~mask;    /* flush the reduce for this token */
 124             }
 125           else
 126             {
 127               /* Matching precedence levels.
 128                  For left association, keep only the reduction.
 129                  For right association, keep only the shift.
 130                  For nonassociation, keep neither.  */
 131
 132               switch (sassoc[i])
 133                 {
 134                 case RIGHT_ASSOC:
 135                   log_resolution (state, lookaheadnum, i, _("shift"));
 136                   break;
 137
 138                 case LEFT_ASSOC:
 139                   log_resolution (state, lookaheadnum, i, _("reduce"));
 140                   break;
 141
 142                 case NON_ASSOC:
 143                   log_resolution (state, lookaheadnum, i, _("an error"));
 144                   break;
 145                 }
 146
 147               if (sassoc[i] != RIGHT_ASSOC)
 148                 {
 149                   *fp2 &= ~mask;        /* flush the shift for this token */
 150                   flush_shift (state, i);
 151                 }
 152               if (sassoc[i] != LEFT_ASSOC)
 153                 {
 154                   *fp1 &= ~mask;        /* flush the reduce for this token */
 155                 }
 156               if (sassoc[i] == NON_ASSOC)
 157                 {
 158                   /* Record an explicit error for this token.  */
 159                   *errtokens++ = i;
 160                 }
 161             }
 162         }
 163
 164       mask <<= 1;
 165       if (mask == 0)
 166         {
 167           mask = 1;
 168           fp2++;
 169           fp1++;
 170         }
 171     }
 172   errp->nerrs = errtokens - errp->errs;
 173   if (errp->nerrs)
 174     {
 175       /* Some tokens have been explicitly made errors.  Allocate
 176          a permanent errs structure for this state, to record them.  */
 177       i = (char *) errtokens - (char *) errp;
 178       err_table[state] = (errs *) xmalloc ((unsigned int) i);
 179       bcopy (errp, err_table[state], i);
 180     }
 181   else
 182     err_table[state] = 0;
 183   free (errp);
 184 }
 185
 186
 187 static void
 188 set_conflicts (int state)
 189 {
 190   int i;
 191   int k;
 192   shifts *shiftp;
 193   unsigned *fp2;
 194   unsigned *fp3;
 195   unsigned *fp4;
 196   unsigned *fp1;
 197   int symbol;
 198
 199   if (consistent[state])
 200     return;
 201
 202   for (i = 0; i < tokensetsize; i++)
 203     lookaheadset[i] = 0;
 204
 205   shiftp = shift_table[state];
 206   if (shiftp)
 207     {
 208       k = shiftp->nshifts;
 209       for (i = 0; i < k; i++)
 210         {
 211           symbol = accessing_symbol[shiftp->shifts[i]];
 212           if (ISVAR (symbol))
 213             break;
 214           SETBIT (lookaheadset, symbol);
 215         }
 216     }
 217
 218   k = lookaheads[state + 1];
 219   fp4 = lookaheadset + tokensetsize;
 220
 221   /* Loop over all rules which require lookahead in this state.  First
 222      check for shift-reduce conflict, and try to resolve using
 223      precedence */
 224   for (i = lookaheads[state]; i < k; i++)
 225     if (rprec[LAruleno[i]])
 226       {
 227         fp1 = LA + i * tokensetsize;
 228         fp2 = fp1;
 229         fp3 = lookaheadset;
 230
 231         while (fp3 < fp4)
 232           {
 233             if (*fp2++ & *fp3++)
 234               {
 235                 resolve_sr_conflict (state, i);
 236                 break;
 237               }
 238           }
 239       }
 240
 241
 242   /* Loop over all rules which require lookahead in this state.  Check
 243      for conflicts not resolved above.  */
 244   for (i = lookaheads[state]; i < k; i++)
 245     {
 246       fp1 = LA + i * tokensetsize;
 247       fp2 = fp1;
 248       fp3 = lookaheadset;
 249
 250       while (fp3 < fp4)
 251         {
 252           if (*fp2++ & *fp3++)
 253             {
 254               conflicts[state] = 1;
 255               any_conflicts = 1;
 256             }
 257         }
 258
 259       fp2 = fp1;
 260       fp3 = lookaheadset;
 261
 262       while (fp3 < fp4)
 263         *fp3++ |= *fp2++;
 264     }
 265 }
 266
 267 void
 268 initialize_conflicts (void)
 269 {
 270   int i;
 271
 272   conflicts = NEW2 (nstates, char);
 273   shiftset = NEW2 (tokensetsize, unsigned);
 274   lookaheadset = NEW2 (tokensetsize, unsigned);
 275
 276   err_table = NEW2 (nstates, errs *);
 277
 278   any_conflicts = 0;
 279
 280   for (i = 0; i < nstates; i++)
 281     set_conflicts (i);
 282 }
 283
 284
 285 /*---------------------------------------------.
 286 | Count the number of shift/reduce conflicts.  |
 287 `---------------------------------------------*/
 288
 289 static void
 290 count_sr_conflicts (int state)
 291 {
 292   int i;
 293   int k;
 294   int mask;
 295   shifts *shiftp;
 296   unsigned *fp1;
 297   unsigned *fp2;
 298   unsigned *fp3;
 299   int symbol;
 300
 301   src_count = 0;
 302
 303   shiftp = shift_table[state];
 304   if (!shiftp)
 305     return;
 306
 307   for (i = 0; i < tokensetsize; i++)
 308     {
 309       shiftset[i] = 0;
 310       lookaheadset[i] = 0;
 311     }
 312
 313   k = shiftp->nshifts;
 314   for (i = 0; i < k; i++)
 315     {
 316       if (!shiftp->shifts[i])
 317         continue;
 318       symbol = accessing_symbol[shiftp->shifts[i]];
 319       if (ISVAR (symbol))
 320         break;
 321       SETBIT (shiftset, symbol);
 322     }
 323
 324   k = lookaheads[state + 1];
 325   fp3 = lookaheadset + tokensetsize;
 326
 327   for (i = lookaheads[state]; i < k; i++)
 328     {
 329       fp1 = LA + i * tokensetsize;
 330       fp2 = lookaheadset;
 331
 332       while (fp2 < fp3)
 333         *fp2++ |= *fp1++;
 334     }
 335
 336   fp1 = shiftset;
 337   fp2 = lookaheadset;
 338
 339   while (fp2 < fp3)
 340     *fp2++ &= *fp1++;
 341
 342   mask = 1;
 343   fp2 = lookaheadset;
 344   for (i = 0; i < ntokens; i++)
 345     {
 346       if (mask & *fp2)
 347         src_count++;
 348
 349       mask <<= 1;
 350       if (mask == 0)
 351         {
 352           mask = 1;
 353           fp2++;
 354         }
 355     }
 356 }
 357
 358
 359 /*----------------------------------------------.
 360 | Count the number of reduce/reduce conflicts.  |
 361 `----------------------------------------------*/
 362
 363 static void
 364 count_rr_conflicts (int state)
 365 {
 366   int i;
 367   int j;
 368   int count;
 369   unsigned mask;
 370   unsigned *baseword;
 371   unsigned *wordp;
 372   int m;
 373   int n;
 374
 375   rrc_count = 0;
 376
 377   m = lookaheads[state];
 378   n = lookaheads[state + 1];
 379
 380   if (n - m < 2)
 381     return;
 382
 383   mask = 1;
 384   baseword = LA + m * tokensetsize;
 385   for (i = 0; i < ntokens; i++)
 386     {
 387       wordp = baseword;
 388
 389       count = 0;
 390       for (j = m; j < n; j++)
 391         {
 392           if (mask & *wordp)
 393             count++;
 394
 395           wordp += tokensetsize;
 396         }
 397
 398       if (count >= 2)
 399         rrc_count++;
 400
 401       mask <<= 1;
 402       if (mask == 0)
 403         {
 404           mask = 1;
 405           baseword++;
 406         }
 407     }
 408 }
 409
 410 /*----------------------------------------------------------.
 411 | Output to OUT a human readable report on shift/reduce and |
 412 | reduce/reduce conflict numbers (SRC_NUM, RRC_NUM).        |
 413 `----------------------------------------------------------*/
 414
 415 static void
 416 conflict_report (FILE *out, int src_num, int rrc_num)
 417 {
 418   if (src_num == 1)
 419     fprintf (out, _(" 1 shift/reduce conflict"));
 420   else if (src_num > 1)
 421     fprintf (out, _(" %d shift/reduce conflicts"), src_num);
 422
 423   if (src_num > 0 && rrc_num > 0)
 424     fprintf (out, _(" and"));
 425
 426   if (rrc_num == 1)
 427     fprintf (out, _(" 1 reduce/reduce conflict"));
 428   else if (rrc_num > 1)
 429     fprintf (out, _(" %d reduce/reduce conflicts"), rrc_num);
 430
 431   putc ('.', out);
 432   putc ('\n', out);
 433 }
 434
 435
 436 /*---------------------------------------------.
 437 | Compute and give a report on the conflicts.  |
 438 `---------------------------------------------*/
 439
 440 void
 441 print_conflicts (void)
 442 {
 443   int i;
 444
 445   src_total = 0;
 446   rrc_total = 0;
 447
 448   /* Count the total number of conflicts, and if wanted, give a
 449      detailed report in FOUTPUT.  */
 450   for (i = 0; i < nstates; i++)
 451     {
 452       if (conflicts[i])
 453         {
 454           count_sr_conflicts (i);
 455           count_rr_conflicts (i);
 456           src_total += src_count;
 457           rrc_total += rrc_count;
 458
 459           if (verboseflag)
 460             {
 461               fprintf (foutput, _("State %d contains"), i);
 462               conflict_report (foutput, src_count, rrc_count);
 463             }
 464         }
 465     }
 466
 467   /* Report the total number of conflicts on STDERR.  */
 468   if (fixed_outfiles)
 469     {
 470       /* If invoked with `--yacc', use the output format specified by
 471          POSIX.  */
 472       fprintf (stderr, _("conflicts: "));
 473       if (src_total > 0)
 474         fprintf (stderr, _(" %d shift/reduce"), src_total);
 475       if (src_total > 0 && rrc_total > 0)
 476         fprintf (stderr, ",");
 477       if (rrc_total > 0)
 478         fprintf (stderr, _(" %d reduce/reduce"), rrc_total);
 479       putc ('\n', stderr);
 480     }
 481   else
 482     {
 483       fprintf (stderr, _("%s contains"), infile);
 484       conflict_report (stderr, src_total, rrc_total);
 485     }
 486 }
 487
 488
 489 void
 490 print_reductions (int state)
 491 {
 492   int i;
 493   int j;
 494   int k;
 495   unsigned *fp1;
 496   unsigned *fp2;
 497   unsigned *fp3;
 498   unsigned *fp4;
 499   int rule;
 500   int symbol;
 501   unsigned mask;
 502   int m;
 503   int n;
 504   int default_LA;
 505   int default_rule = 0;
 506   int cmax;
 507   int count;
 508   shifts *shiftp;
 509   errs *errp;
 510   int nodefault = 0;
 511
 512   for (i = 0; i < tokensetsize; i++)
 513     shiftset[i] = 0;
 514
 515   shiftp = shift_table[state];
 516   if (shiftp)
 517     {
 518       k = shiftp->nshifts;
 519       for (i = 0; i < k; i++)
 520         {
 521           if (!shiftp->shifts[i])
 522             continue;
 523           symbol = accessing_symbol[shiftp->shifts[i]];
 524           if (ISVAR (symbol))
 525             break;
 526           /* if this state has a shift for the error token,
 527              don't use a default rule.  */
 528           if (symbol == error_token_number)
 529             nodefault = 1;
 530           SETBIT (shiftset, symbol);
 531         }
 532     }
 533
 534   errp = err_table[state];
 535   if (errp)
 536     {
 537       k = errp->nerrs;
 538       for (i = 0; i < k; i++)
 539         {
 540           if (!errp->errs[i])
 541             continue;
 542           symbol = errp->errs[i];
 543           SETBIT (shiftset, symbol);
 544         }
 545     }
 546
 547   m = lookaheads[state];
 548   n = lookaheads[state + 1];
 549
 550   if (n - m == 1 && !nodefault)
 551     {
 552       default_rule = LAruleno[m];
 553
 554       fp1 = LA + m * tokensetsize;
 555       fp2 = shiftset;
 556       fp3 = lookaheadset;
 557       fp4 = lookaheadset + tokensetsize;
 558
 559       while (fp3 < fp4)
 560         *fp3++ = *fp1++ & *fp2++;
 561
 562       mask = 1;
 563       fp3 = lookaheadset;
 564
 565       for (i = 0; i < ntokens; i++)
 566         {
 567           if (mask & *fp3)
 568             fprintf (foutput, _("    %-4s\t[reduce using rule %d (%s)]\n"),
 569                      tags[i], default_rule, tags[rlhs[default_rule]]);
 570
 571           mask <<= 1;
 572           if (mask == 0)
 573             {
 574               mask = 1;
 575               fp3++;
 576             }
 577         }
 578
 579       fprintf (foutput, _("    $default\treduce using rule %d (%s)\n\n"),
 580                default_rule, tags[rlhs[default_rule]]);
 581     }
 582   else if (n - m >= 1)
 583     {
 584       cmax = 0;
 585       default_LA = -1;
 586       fp4 = lookaheadset + tokensetsize;
 587
 588       if (!nodefault)
 589         for (i = m; i < n; i++)
 590           {
 591             fp1 = LA + i * tokensetsize;
 592             fp2 = shiftset;
 593             fp3 = lookaheadset;
 594
 595             while (fp3 < fp4)
 596               *fp3++ = *fp1++ & (~(*fp2++));
 597
 598             count = 0;
 599             mask = 1;
 600             fp3 = lookaheadset;
 601             for (j = 0; j < ntokens; j++)
 602               {
 603                 if (mask & *fp3)
 604                   count++;
 605
 606                 mask <<= 1;
 607                 if (mask == 0)
 608                   {
 609                     mask = 1;
 610                     fp3++;
 611                   }
 612               }
 613
 614             if (count > cmax)
 615               {
 616                 cmax = count;
 617                 default_LA = i;
 618                 default_rule = LAruleno[i];
 619               }
 620
 621             fp2 = shiftset;
 622             fp3 = lookaheadset;
 623
 624             while (fp3 < fp4)
 625               *fp2++ |= *fp3++;
 626           }
 627
 628       for (i = 0; i < tokensetsize; i++)
 629         shiftset[i] = 0;
 630
 631       if (shiftp)
 632         {
 633           k = shiftp->nshifts;
 634           for (i = 0; i < k; i++)
 635             {
 636               if (!shiftp->shifts[i])
 637                 continue;
 638               symbol = accessing_symbol[shiftp->shifts[i]];
 639               if (ISVAR (symbol))
 640                 break;
 641               SETBIT (shiftset, symbol);
 642             }
 643         }
 644
 645       mask = 1;
 646       fp1 = LA + m * tokensetsize;
 647       fp2 = shiftset;
 648       for (i = 0; i < ntokens; i++)
 649         {
 650           int defaulted = 0;
 651
 652           if (mask & *fp2)
 653             count = 1;
 654           else
 655             count = 0;
 656
 657           fp3 = fp1;
 658           for (j = m; j < n; j++)
 659             {
 660               if (mask & *fp3)
 661                 {
 662                   if (count == 0)
 663                     {
 664                       if (j != default_LA)
 665                         {
 666                           rule = LAruleno[j];
 667                           fprintf (foutput,
 668                                    _("    %-4s\treduce using rule %d (%s)\n"),
 669                                    tags[i], rule, tags[rlhs[rule]]);
 670                         }
 671                       else
 672                         defaulted = 1;
 673
 674                       count++;
 675                     }
 676                   else
 677                     {
 678                       if (defaulted)
 679                         {
 680                           rule = LAruleno[default_LA];
 681                           fprintf (foutput,
 682                                    _("    %-4s\treduce using rule %d (%s)\n"),
 683                                    tags[i], rule, tags[rlhs[rule]]);
 684                           defaulted = 0;
 685                         }
 686                       rule = LAruleno[j];
 687                       fprintf (foutput,
 688                                _("    %-4s\t[reduce using rule %d (%s)]\n"),
 689                                tags[i], rule, tags[rlhs[rule]]);
 690                     }
 691                 }
 692
 693               fp3 += tokensetsize;
 694             }
 695
 696           mask <<= 1;
 697           if (mask == 0)
 698             {
 699               mask = 1;
 700               /* We tried incrementing just fp1, and just fp2; both seem wrong.
 701                  It seems necessary to increment both in sync.  */
 702               fp1++;
 703               fp2++;
 704             }
 705         }
 706
 707       if (default_LA >= 0)
 708         {
 709           fprintf (foutput, _("    $default\treduce using rule %d (%s)\n"),
 710                    default_rule, tags[rlhs[default_rule]]);
 711         }
 712
 713       putc ('\n', foutput);
 714     }
 715 }
 716
 717
 718 void
 719 finalize_conflicts (void)
 720 {
 721   FREE (conflicts);
 722   FREE (shiftset);
 723   FREE (lookaheadset);
 724 }